Such pumps can be, for instance, part of power steering assist systems in motor vehicles in which they generate the hydraulic pressure of a servo liquid for a piston-cylinder configuration which supports the required steering forces at the steering wheel of a motor vehicle. In another example, they can also be part of the vehicle transmission were they provide the hydraulic pressure of a transmission oil to lubricate and/or activate (changing of a gear ratio, engaging/disengaging of transmission shafts) in the motor vehicle transmission. Preferably, this is a vane type pump as described in DE 39 28 029 A1 and in DE 41 38 516 A1, and where the content is in here fully disclosed. Such vane type pumps draw the oil out of a supply container, which is external to the pump, and are usually equipped with a flow controlling valve through which the oil is conveyed from the high-pressure area to the intake of the pump. Starting at a certain pump rotational speed or rather a certain flow rate, the flow control valve opens so that the oil, which is at high-pressure, can exit in to a pressure duct through which it passes into the suction area of the pump.
Known from DE 41 38 516 A1 is an intake charged pump which, to guarantee highly reliable and low noise operation and while preventing the creation of cavities and sound from drawn in air bubbles, is equipped with an additional injector at high oil pressure, and through which the oil can be channeled from the intake channel into the intake of the pump. Hereby, adequate filling of the intake of the pump shall be achieved under all operating conditions and, due to the adequate supply of oil to the intake, damages which are caused by cavities can be avoided. The embodiment example which is presented and described therein refers to the fact that the center axis of the injector matches the center axis of a channel section which leads into the intake of the pump, and also matches a center axis of an output bore of the flow control valve. It is also mentioned and noted that it is possible to pivot the center axis of the injector with respect to the other two axes, for instance to the right, so that the fluid which is under high-pressure and flowing through the injector, as well as its entrained oil, and that the intake of the pump, even with a different configuration of the parts, can be filled at an optimum with fluid to be transported.
In addition to DE 41 38 516 A1, the document DE 198 36 628 A1 mentions that the injector device is effective just at one side of the housing with a jet nozzle and from there on needs to direct the fluid from a tank to both sides of the enclosure to the respective intake, to provide the fluid for the suction pockets which are positioned on both sides of the transport device or the rotational group, respectively, in an adequate level. Due to the different lengths of the flow paths to the suction pockets on both sides, different pressure conditions occur in the fluid, which causes different load levels at the suction pockets on both sides. This causes, especially at large transport outputs of the pump, the cavities or rather damage due to cavities. In addition, an equal filling of the suction areas on both sides is doubtful.
To avoid these problems, DE 198 36 628 A1 proposes that the feed duct on both sides of the transport device each leads with one partial duct into a jet chamber, and that the injector device emits the oil on both sides so that at least one jet nozzle is aiming into each of the two jet chambers of the injector device. From that point, the fluid flows, via branching intake ducts, to diametrically opposed suction pockets of a dual-chamber vane type pump, which are mainly designed as having equal lengths so that the same pressure conditions in the suction area and the same fluid volume is provided at both sides. However, the fluid which is ejected from the jet nozzles hits a perpendicular wall of the jet chambers which results in a loss of kinetic energy and prevents an even pressure reduction in the direction of the suction pockets.
Although DE 102 16 549 A1 mentions that a pump of a similar type includes flow separators for the oil return flow which divide the oil return flow in a way such that the partial flows have the same energy content and load pressure at all suction pockets so that in particular the same energy content of the flow, as well as the same load pressure can be provided to all four suction pockets. This arrangement also requires sharp redirecting edges and impact surfaces which create losses of kinetic energy of the stream.
The previously mentioned vane type pumps or roller cell pumps, however, are designed in a compact manner, but have the previously mentioned disadvantages due to their compactness.